The present invention relates to a liquid crystalline compound and liquid crystal composition. More specifically, it relates to a novel liquid crystalline compound which has an alkenylene group having 2 to 4 carbon atoms and ester bond as bonding group at the same time, relates to a liquid crystal composition comprising the compound, and relates to a liquid crystal display device comprising the liquid crystal composition.
Liquid crystal display devices comprising liquid crystalline compounds (the term xe2x80x9cliquid crystalline compoundxe2x80x9d as used hereinafter is intended to use as a general name for compounds exhibiting a liquid crystal phase, or compounds which do not exhibit a liquid crystal phase but are useful as a component of liquid crystal compositions) are widely used in displays such as watches, tabletop calculators, and word processors. These display devices utilize optical anisotropy and dielectric anisotropy of liquid crystalline compounds.
Liquid crystal phase includes nematic liquid crystal phase, smectic liquid crystal phase, and cholesteric liquid crystal phase, and display devices utilizing nematic liquid crystal phase are most widely used.
As display mode using a liquid crystal, there have been devised dynamic scattering (DS) mode, deformation of aligned phases (DAP) mode, guest/host (GH) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, and thin film transistor (TFT) mode.
Liquid crystalline compounds used in these display devices have to exhibit liquid crystal phase in a wide temperature range with room temperature being its center, have to be sufficiently stable under conditions in which the display devices are used, and have to have properties sufficient to drive the display devices. However, no liquid crystalline compounds which satisfy these requirements by a single compound have been found up to now. Accordingly, it is actual circumstances that several kind or several tens kind of liquid crystalline compounds are mixed to produce liquid crystal compositions having required properties. These liquid crystal compositions are required to be stable against moisture, light, heat, and air which usually present under conditions in which the display devices are used, required to be stable against electric field and electromagnetic radiation, and further required to be chemically stable against the compounds to be mixed. The liquid crystal compositions are required to have proper values of such physical properties as optical anisotropy (xcex94n) and dielectric anisotropy (xcex94xcex5) depending on display mode and the shape of display devices. Further, it is important that each component in the liquid crystal compositions has an excellent solubility with one another.
Especially, it is desired to still more lower threshold voltage which largely contributes to high speed response necessary for expanding the size of screen of liquid crystal display, and contributes to saving of electric power (E. Jakeman et al., Phys. Lett., 39A. 69 (1972)). For the high speed response, low viscosity of the compositions is also important. Moreover, environments in which liquid crystal display devices are used are diversified in recent years, and keeping with such circumstance, development of liquid crystalline compounds which exhibit liquid crystal phase in a wider temperature range is earnestly desired.
In order to achieve these purposes, various compounds have heretofore been developed, for instance, the compound expressed by the following formula (a) or (b) is proposed in Laid-open Japanese Patent Publication No. Hei 4-279560, and the compound expressed by the following formula (c) is proposed in Japanese Patent Publication No. Hei 7-72148, respectively.
However, the compound expressed by the formula (a) can not be said to be sufficiently wide in temperature range of liquid crystal phase, and the compound expressed by the formula (b) has a problem that its viscosity is high.
Whereas the compound expressed by the formula (c) is a three ring compound containing an alkenylene group as bonding group, its disclosure is insufficient. That is, the physical properties of the compound are not shown, and besides, specific data are not disclosed at all about the utility expected when it is used as a component of liquid crystal compositions. 
An object of the present invention is to remove the problems in the background art described above. Another object of the present invention is to provide novel liquid crystalline compounds which are wide in temperature range of liquid crystal phase, are low in viscosity, have a low threshold voltage, and are excellent in stability and mutual solubility with other liquid crystal materials, to provide liquid crystal compositions comprising the liquid crystalline compound, and to provide liquid crystal display devices comprising the liquid crystal composition.
The present invention for achieving the purposes described above is summarized as follows:
(1) A vinylene compound expressed by the general formula (1)
Raxe2x80x94A1xe2x80x94Z1xe2x80x94A2xe2x80x94Z2xe2x80x94A3xe2x80x94(Z3xe2x80x94A4)mxe2x80x94Rbxe2x80x83xe2x80x83(1)
wherein Ra represents an alkyl group having 1 to 20 carbon atoms one or more xe2x80x94CH2xe2x80x94 in which alkyl group may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or xe2x80x94Cxe2x95x90Cxe2x80x94, but in no case xe2x80x94Oxe2x80x94 and/or xe2x80x94Sxe2x80x94 continues, and one or more hydrogen atoms in which alkyl group may be replaced by a halogen atom; Rb represents Ra, a halogen atom, or cyano group; A1, A2, A3, and A4 independently represent trans-1,4-cyclohexylene group, cyclohexenylene group, 1,4-phenylene group one or more hydrogen atoms on which ring may be replaced by a halogen atom or cyano group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, or 1,3-dioxane-2,5-diyl group; Z1, Z2, and Z3 independently represent an alkenylene group having 2 to 4 carbon atoms, xe2x80x94COOxe2x80x94, xe2x80x94OCOxe2x80x94, xe2x80x94(CH2)2xe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, or a covalent bond provided that at least one of Z1 to Z3 represents an alkenylene group having 2 to 4 carbon atoms, and at least one of Z1 to Z3 represents xe2x80x94COOxe2x80x94 or xe2x80x94OCOxe2x80x94; and m is 0 or 1.
(2) The vinylene compound recited in (1) above wherein m is 0.
(3) The vinylene compound recited in (1) above wherein m is 1.
(4) The vinylene compound recited in (2) above wherein either Z1 or Z2 is vinylene or butenylene.
(5) The vinylene compound recited in (3) above wherein either Z1 or Z2 is vinylene or butenylene.
(6) The vinylene compound recited in (4) above wherein A1 and A2 are independently trans-1,4-cyclohexylene group, or 1,4-phenylene group one or more hydrogen atoms on which ring may be replaced by a halogen atom or cyano group.
(7) The vinylene compound recited in (5) above wherein A1 and A2 are independently trans-1,4-cyclohexylene group, or 1,4-phenylene group one or more hydrogen atoms on which ring may be replaced by a halogen atom or cyano group.
(8) A liquid crystal composition comprising at least one vinylene compound recited in any one of (1) to (7) above.
(9) A liquid crystal composition comprising, as a first component, at least one vinylene compound recited in any one of (1) to (7) above, and comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (2), (3), and (4) 
wherein R1 represents an alkyl group having 1 to 10 carbon atoms; X1 represents F, Cl, OCF3, OCF2H, CF3, CF2H, or CFH2; L1, L2, L3, and L4 independently represent H or F; Z4 and Z5 independently represent xe2x80x94(CH2)2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or a covalent bond; and a is 1 or 2.
(10) A liquid crystal composition comprising, as a first component, at least one vinylene compound recited in any one of (1) to (7) above, and comprising, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (5), (6), (7), (8), and (9) 
wherein R2 represents F, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms any methylene group (xe2x80x94CH2xe2x80x94) in which alkyl or alkenyl group may be replaced by oxygen atom (xe2x80x94Oxe2x80x94), but in no case two or more methylene groups are continuously replaced by oxygen atom; ring A represents trans-1,4-cyclohexylene group, 1,4-phenylene group, or 1,3-dioxane-2,5-diyl group; ring B represents trans-1,4-cyclohexylene group, 1,4-phenylene group, or pyrimidine-2,5-diyl group; ring C represents trans-1,4-cyclohexylene group or 1,4-phenylene group; Z6 represents xe2x80x94(CH2)2xe2x80x94, xe2x80x94COOxe2x80x94, or a covalent bond; L5 and L6 independently represent H or F; and b and c are independently 0 or 1, 
wherein R3 represents an alkyl group having 1 to 10 carbon atoms, L7 represents H or F; and d is 0 or 1, 
wherein R4 represents an alkyl group having 1 to 10 carbon atoms; ring D and ring E independently represent trans-1,4-cyclohexylene group or 1,4-phenylene group; Z7 and Z8 independently represent xe2x80x94COOxe2x80x94 or a covalent bond; Z9 represents xe2x80x94COOxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94; L8 and L9 independently represent H or F; X2 represents F, OCF3, OCF2H, CF3, CF2H, or CFH2; and e, f, and g are independently 0 or 1, 
wherein R5 and R6 independently represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms any methylene group (xe2x80x94CH2xe2x80x94) in which alkyl or alkenyl group may be replaced by oxygen atom (xe2x80x94Oxe2x80x94), but in no case two or more methylene groups are continuously replaced by oxygen atom; ring G represents trans-1,4-cyclohexylene group, 1,4-phenylene group, or pyrimidine-2,5-diyl group; ring H represents trans-1,4-cyclohexylene group or 1,4-phenylene group; Z10 represents xe2x80x94Cxe2x89xa1Cxe2x80x94xe2x80x94COOxe2x80x94, xe2x80x94(CH2)2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94Cxe2x89xa1Cxe2x80x94or a covalent bond; and Z11 represents xe2x80x94COOxe2x80x94 or a covalent bond, 
wherein R7 and R8 independently represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms any methylene group (xe2x80x94CH2xe2x80x94) in which alkyl or alkenyl group may be replaced by oxygen atom (xe2x80x94Oxe2x80x94), but in no case two or more methylene group are continuously replaced by oxygen atom; ring I represents trans-1,4-cyclohexylene group, 1,4-phenylene group, or pyrimidine-2,5-diyl group; ring J represents trans-1,4-cyclohexylene group, 1,4-phenylene group one or more hydrogen atoms on which ring may be replaced by F, or pyrimidine-2,5-diyl group; ring K represents trans-1,4-cyclohexylene group or 1,4-phenylene group; Z12 and Z14 independently represent xe2x80x94COOxe2x80x94, xe2x80x94(CH2)2xe2x80x94, or a covalent bond; Z13 represents xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94COOxe2x80x94, or a covalent bond; and h is 0 or 1.
(11) A liquid crystal composition comprising, as a first component, at least one vinylene compound recited in any one of (1) to (7) above, comprising, as a part of a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (2), (3), and (4), and comprising, as another part of the second component, at least one compound selected from the group consisting of the compounds expressed by any one of the general formulas (5), (6), (7), (8), and (9).
(12) A liquid crystal display device comprising the liquid crystal composition recited in any one of (8) to (11) above.
Liquid crystalline vinylene compounds of the present invention expressed by the general formula (1) are wide in temperature range of liquid crystal phase, are low in viscosity, and have a low threshold voltage. These liquid crystalline compounds are sufficiently stable chemically and physically under the conditions in which liquid crystal display devices are ordinarily used. Further, liquid crystalline compounds having desired physical properties can be obtained by selecting proper rings, substituents and/or bonding groups from molecule forming elements.
Accordingly, when the compounds of the present invention are used as component of liquid crystal compositions, novel liquid crystal compositions having preferable properties can be provided.
Liquid crystalline compounds of the present invention expressed by the general formula (1) are classified as shown below. In the formulas shown below, ak represents an alkenylene group having 2 to 4 carbon atoms, E represents ester bond, and Ra, Rb, A1 to A4, and Z1 to Z3 have the same meaning as defined above.
Compounds having three six-membered rings:
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94Rbxe2x80x83xe2x80x83(1a)
Raxe2x80x94A1xe2x80x94Exe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Rbxe2x80x83xe2x80x83(1b)
Compounds having four six-membered rings:
Raxe2x80x94A1xe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1c)
Raxe2x80x94A1xe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94akxe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1d)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1e)
Raxe2x80x94A1xe2x80x94Exe2x80x94A2xe2x80x94A3xe2x80x94akxe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1f)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1g)
Raxe2x80x94A1xe2x80x94Exe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1h)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1i)
Raxe2x80x94A1xe2x80x94Exe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94akxe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1j)
Raxe2x80x94A1xe2x80x94(CH2)2xe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1k)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94(CH2)2xe2x80x94A2xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1l)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94(CH2)2xe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1m)
Raxe2x80x94A1xe2x80x94Exe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94(CH2)2xe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1n)
xe2x80x83Raxe2x80x94A1xe2x80x94Cxe2x89xa1Cxe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1o)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Cxe2x89xa1Cxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1p)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94Cxe2x89xa1Cxe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1q)
Raxe2x80x94A1xe2x80x94CH2Oxe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1r)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94CH2Oxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1s)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94CH2Oxe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1t)
Raxe2x80x94A1xe2x80x94OCH2xe2x80x94A2xe2x80x94akxe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1u)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94OCH2xe2x80x94A3xe2x80x94Exe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1v)
Raxe2x80x94A1xe2x80x94akxe2x80x94A2xe2x80x94Exe2x80x94A3xe2x80x94OCH2xe2x80x94A4xe2x80x94Rbxe2x80x83xe2x80x83(1w)
While the compounds expressed by one of the formulas (1a) to (1w) are preferable, the compounds expressed by one of the following formulas (1Xa) to (1Xq) are especially preferable among the former compounds: 
wherein Ra, Rb, A2 to A4, Z2, Z3, and m have the same meaning as described above.
As described above, the liquid crystalline compounds of the present invention are expressed by the general formula (1).
In the formula, Ra is a straight chain or branched alkyl group having 1 to 20 carbon atoms. As the straight chain alkyl group, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, decyl, pentadecyl, and icosyl can specifically be mentioned. As the branched alkyl group, isopropyl, 2-methylbutyl, sec-butyl, tert-butyl, isopentyl, isohexyl, 3-ethyloctyl, 3,8-dimethyltetradecyl, and 5-ethyl-5-methylnonadecyl can specifically be mentioned. The branched alkyl groups described above may be ones which exhibit an optical activity.
One or more xe2x80x94CH2xe2x80x94 in these alkyl groups may be replaced by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or xe2x80x94Cxe2x89xa1Cxe2x80x94, unless xe2x80x94Oxe2x80x94 and/or xe2x80x94Sxe2x80x94 continues. Among the alkyl groups, alkoxy groups and alkoxyalkyl groups can be mentioned as examples in which xe2x80x94CH2xe2x80x94 is replaced by xe2x80x94Oxe2x80x94; alkylthioalkyl groups as examples in which xe2x80x94CH2xe2x80x94 is replaced by xe2x80x94Sxe2x80x94; alkenyl groups, alkoxyalkenyl groups, alkenyloxy groups, alkenyloxyalkyl groups, and alkadienyl groups as examples in which xe2x80x94CH2xe2x80x94 is replaced by xe2x80x94CHxe2x95x90CHxe2x80x94; and alkynyl groups, alkynyloxy groups, and alkoxyalkynyl groups as examples in which xe2x80x94CH2xe2x80x94 is replaced by xe2x80x94Cxe2x89xa1Cxe2x80x94. One or more hydrogen atoms in the alkyl groups described above may be replaced by a halogen atom, and halogen substituted alkyl groups, halogen substituted alkoxy groups, halogen substituted alkenyl groups, and halogen substituted alkynyl groups can be mentioned as their examples.
Specific examples of these substituted alkyl groups are as follows:
As alkoxy groups, such groups as methoxy, ethoxy, propoxy, butoxy, pentyloxy, and nonyloxy,
as alkoxyalkyl groups, such groups as methoxymethyl, methoxyethyl, methoxypropyl, methoxybutyl, methoxypentyl, methoxyoctyl, ethoxymethyl, ethoxyethyl, ethoxypropyl, ethoxyhexyl, propoxymethyl, propoxyethyl, propoxypropyl, propoxypentyl, butoxymethyl, butoxyethyl, butoxybutyl, pentyloxymethyl, pentyloxybutyl, hexyloxymethyl, hexyloxyethyl, hexyloxypropyl, heptyloxymethyl, and octyloxymethyl,
as alkylthioalkyl groups, such groups as methylthiomethyl, methylthioethyl, methylthiopropyl, methylthiobutyl, methylthiooctyl, ethylthiomethyl, ethylthioethyl, ethylthioheptyl, propylthiomethyl, propylthioethyl, propylthiopropyl, propylthiopentyl, hexylthiomethyl, and heptylthioethyl,
as the groups in which xe2x80x94COxe2x80x94 substituted, such groups as methylcarbonyl, ethylcarbonyl, propylcarbonyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, heptyloxycarbonyl, 2-oxopropyl, 2-oxobutyl, 3-oxobutyl, 2-oxopentyl, 4-oxopentyl, 3-oxohexyl, 5-oxohexyl, 2-oxoheptyl, 3-oxoheptyl, 6-oxoheptyl, 2-oxooctyl, 4-oxooctyl, 7-oxooctyl, 3-oxononyl, 6-oxononyl, 8-oxononyl, 2-oxodecyl, 5-oxodecyl, and 9-oxodecyl,
as alkenyl groups, such groups as vinyl, propenyl, butenyl, pentenyl, hexenyl, and decenyl,
as alkoxyalkenyl groups, such groups as methoxypropenyl, ethoxypropenyl, pentyloxypropenyl, methoxybutenyl, ethoxybutenyl, pentyloxybutenyl, methoxypentenyl, propoxypentenyl, methoxyhexenyl, propoxyhexenyl, methoxyheptenyl, and methoxyoctenyl,
as alkenyloxy groups, such groups as propenyloxy, butenyloxy, pentenyloxy, octenyloxy, and propenyloxymethyl,
as alkenyloxyalkyl groups, such groups as propenyloxyethyl, propenyloxybutyl, butenyloxymethyl, butenyloxyethyl, butenyloxypentyl, pentenyloxymethyl, pentenyloxypropyl, hexenyloxymethyl, hexenyloxyethyl, heptenyloxymethyl, and octenyloxymethyl,
as alkadienyl groups, such groups as butadienyl, pentadienyl, hexadienyl, heptadienyl, octadienyl, and icosadienyl,
as alkynyl groups, such groups as ethynyl, propynyl, butynyl, pentynyl, and octynyl,
as alkynyloxy groups, such groups as ethynyloxy, propynyloxy, butynyloxy, pentynyloxy, and tetradecynyloxy,
as alkoxyalkynyl groups, methoxypropynyl, methoxypentynyl, ethoxybutynyl, propoxypropynyl, hexyloxyheptynyl, methoxymethylbutynyl, methoxypropylethynyl, and butoxymethylpropynyl,
as halogen substituted alkyl groups, such groups as fluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 1,2-difluoroethyl, 1,1,2,2-tetrafluoroethyl, 2-bromo-1,2-difluoroethyl, 3-fluoropropyl, 1,2,3,3-tetrafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, 4-fluorobutyl, 1,1,2,4-tetrafluorobutyl, 5-fluoropentyl, 2,3,3,4,5-pentafluoropentyl, 6-fluorohexyl, 2,3,4,6-tetrafluorohexyl, 7-fluoroheptyl, and 8,8-difluorooctyl,
as halogen substituted alkoxy groups, such groups as difluoromethoxy, trifluoromethoxy, 1,1-difluoroethoxy, 2,2-difluoroethoxy, 2,2,2-trifluoroethoxy, 1,1,2,2-tetrafluoroethoxy, perfluoroethoxy, 1,1,2,3,3,3-hexafluoropropoxy, and perfluoropropoxy, and
as halogen substituted alkenyl groups, such groups as 3-fluoropropenyl, 4-fluoro-1-butenyl, 4-fluoro-2-butenyl, 5-fluoro-1-pentenyl, 5-fluoro-2-pentenyl, 5-fluoro-3-pentenyl, 6-fluoro-1-hexenyl, 6-fluoro-3-hexenyl, 7-fluoro-5-heptenyl, 2,2-difluorovinyl, 1,2-difluorovinyl, 2-chloro-2-fluorovinyl, 2-bromo-2-fluorovinyl, 2-fluoro-2-cyanovinyl, 3,3-difluoro-2-propenyl, 3-chloro-3-fluoro-1-propenyl, 2,3-difluoro-1-propenyl, 1,3-difluoro-2-propenyl, 1,3,3-trifluoro-2-propenyl, 1,2,4,4-tetrafluoro-3-butenyl, 5,5-difluoro-4-pentenyl, 3,3-difluoro-5-hexenyl, and 8,8-difluoro-7-octenyl.
While Rb is a group selected from the Ra described above, a member selected from halogen atoms including F, Cl, Br, and I, or cyano group, it is preferably F, Cl, or cyano group from the viewpoint, for example, of stability.
A1, A2, A3, and A4 are independently selected from trans-1,4-cyclohexylene group, cyclohexenylene group, 1,4-phenylene group one or more hydrogen atoms on which ring may be replaced by a halogen atom or cyano group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, or 1,3-dioxane-2,5-diyl group.
Among the groups in which one or more hydrogen atoms may be replaced by a halogen atom or cyano group, for example, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, 2,3-5-trifluoro-1,4-phenylene, 2-chloro-1,4-phenylene, 3-chloro-1,4-phenylene, 2,3-dichloro-1,4-phenylene, 3,5-dichloro-1,4-phenylene, 3-bromo-1,4-phenylene, 2-iodo-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene, 3-fluoro-5-chloro-1,4-phenylene, 2-cyano-1,4-phenylene, 3-cyano-1,4-phenylene, and 2,3-dicyano-1,4-phenylene can be mentioned as examples in which the ring is 1,4-phenylene.
At least one of Z1, Z2, and Z3 is an alkenylene group having 2 to 4 carbon atoms, vinylene or butenylene can be mentioned as their preferable examples, and the vinylene or butenylene in which alkenylene group is in trans form can be mentioned as more preferable examples.
Compounds of the present invention expressed by the general formula (1) and constituted by the groups selected from the Ra, Rb, A1 to A4, and Z1 to Z3 described above have preferable properties. Among them, the compounds which do not have two or more rings containing a hetero atom, and are expressed by one of the formulas (1Xa) to (1Xq) are more preferable.
As more specific examples of these compounds, the ones expressed by one of the following formulas (1-1) to (1-47) can be mentioned: 
wherein Ra and Rb have the same meaning as described above, and hydrogen atom on the ring may independently be replaced by the atom or group shown in the parenthesis.
Compounds of the present invention expressed by the general formula (1) can easily be produced by known general methods of organic synthesis, for instance, by the following methods: 
wherein Ra, Rb, A1 to A4, Z3, and m have the same meaning as described above.
For instance, a compound (1) which is an example of the compounds of the present invention can be produced by reacting a carboxylic acid derivative (2) with an alcohol (including phenol) derivative (3) in a solvent such as dichloromethane and chloroform in the presence of a dehydrating agent such as dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP) (B. Neises et al., Organic Synthesis, 63, 183 (1985)).
The compound (1) can also be produced by the method of E. J. Corey et al. (The Journal of Organic Chemistry, 38, 3223 (1973)), that is, by converting the carboxylic acid derivative (2) described above into a compound (4) with a halogenating agent such as thionyl chloride in the presence or absence of a solvent such as toluene and benzene, and then reacting the compound (4) with the alcohol derivative (3) described above. This reaction is carried out at a temperature from room temperature to the boiling point of the solvent and under an inert gas atmosphere, more preferably, for accelerating the reaction, in the presence of a base such as pyridine, triethylamine (B. Iselin et al., Helvetica Chimica Acta, 40, 373 (1957)), dimethylaniline (C. Raha, Organic Synthesis, IV, 263 (1963)), or tetramethylurea (M. S. Newman et al., Tetrahedron Letters, 3267 (1967)).
Introduction of carbonyloxy group to the carboxylic acid derivative (2) used as a starting material in the reaction described above can be performed by known general procedures of organic synthesis or their combination. For instance, it can readily be carried out by such methods as the hydrolysis of a nitrile derivative (R. C. Fuson et al., Organic Synthesis, III, 557 (1955); and P. C. Baraldi et al., The Journal of Organic Chemistry, 50, 23 (1985)), the reaction of a Grignard reagent or lithium compound with carbon dioxide (H. Gilman et al., Organic Synthesis, I, 361 (1941); and Y. Fukuyama et al., Synthesis, 443 (1974)), the hydrolysis of an acid halide (N. O. V. Sonntag, Chemical Review, 52, 237 (1953)), or the oxidation of an alkyl, alcohol, or aldehyde derivative (L. Friedman, Organic Synthesis, V, 810 (1973); E. Turos et al., Journal of the American Chemical Society, 111, 8231 (1989); R. L. Shriner et al., Organic Synthesis, II, 538 (1943); D. Vakentine, Jr. et al., The Journal of Organic Chemistry, 45, 3698 (1980); E. Dalcanale et al., The Journal of Organic Chemistry, 51, 567 (1986); and E. J. Corey et al., Tetrahedron Letters, 399 (1979).
Introduction of xe2x80x94CHxe2x95x90CHxe2x80x94 can readily be carried out, for instance, by the Wittig reaction (Organic Reactions, Vol. 14, Chapter 3), the Wittig-Schlosser reaction (M. Schlosser et al., Angew. Chem., International Edition in English, 5, 126 (1966), or the Wittig-Horner reaction (J. I. G. Cadogan, Organophosphorus Reagents in Organic Synthesis, Academic (1979)).
That is, compounds in which xe2x80x94CHxe2x95x90CHxe2x80x94 is introduced can be produced by reacting an aldehyde with a phosphonium salt in a solvent such as tetrahydrofuran and diethyl ether in the presence of a base such as potassium-tert-butoxide (t-BuOK) and n-butyl lithium. This reaction is preferably carried out at a temperature from room temperature to xe2x88x9250xc2x0 C. under an inert gas atmosphere. It is possible to isomerize the compounds thus obtained by reacting them with benzenesulfinic acid or p-toluenesulfinic acid.
Further, xe2x80x94CHxe2x95x90CHxe2x80x94 can be introduced by a method in which a vinyl Grignard reagent and a halide are subjected to a coupling reaction in the presence of a catalyst such as Pd(PPh3)4, PdCl2(PPh3)2, or NiCl2(dppp) (T. V. Lee et al., Tetrahedron Letters, 46, 921 (1990)), or a method in which an aldehyde and a Grignard reagent are reacted, and the product thus formed is heated to dehydrate in a solvent such as toluene and xylene in the presence of an acidic catalyst such as p-toluenesulfonic acid.
Introduction of xe2x80x94Cxe2x89xa1Cxe2x80x94 can be carried out, for instance, by the method of W. Tao et al. (The Journal of Organic Chemistry, 55, 63 (1990), that is, by reacting an acetylene derivative with a halide in an alkylamine solvent such as diethylamine and triethylamine in the presence of a copper iodide and a Pd catalyst such as Pd(PPh3)4 and PdCl2(PPh3)2. This reaction is preferably performed at a temperature from room temperature to the boiling point of the solvent and under an inert gas atmosphere. It can be introduced also by the Castro reaction (M. D. Raush et al., The Journal of Organic Chemistry, 34, 468 (1969).
Introduction of xe2x80x94Oxe2x80x94 can be carried out, for instance, by reacting a halide with an alcohol or phenol derivative in a solvent such as dimethyl sulfoxide, dimethyl formamide, 1,2-dimethoxyethane, tetrahydrofuran, hexamethylphosphoric acid triamide, and toluene in the presence of a base such as sodium amide (J. B. Wright et al., Journal of the American Chemical Society, 70, 3098 (1948)), potassium carbonate (W. T. Olson et al., Journal of the American Chemical Society, 69, 2451 (1947)), triethylamine (R. L. Merker et al., The Journal of Organic Chemistry, 26, 5180 (1961), sodium hydroxide (C. Wilkins, Synthesis, 1973, 156), potassium hydroxide (J. Rebek et al., The Journal of Organic Chemistry, 44, 1485 (1979), barium hydroxide (Kawabe et al., The Journal of Organic Chemistry, 37, 4210 (1972)), or sodium hydride (C. J. Stark, Tetrahedron Letters, 22, 2089 (1981); and K. Takai et al., Tetrahedron Letters, 21, 1657 (1980)).
While general methods for producing the compounds of the present invention are described above, more specific examples for producing starting materials, carboxylic acid derivatives and alcohol derivatives are described below.
Production of carboxylic acid derivatives:
As shown in scheme 1, compound (5) which is prepared by a method described, for example, in Japanese Patent Publication No. Hei 7-2653 is converted into compound (6) by reacting with an alcohol such as methanol and ethanol in the presence of pyridinium dichromate (PDC). Subsequently, this compound is reacted with methoxymethylphosphonium chloride (MOTP) in the presence of a base such as potassium-tert-butoxide (t-BuOK) and then deprotected with a diluted hydrochloric acid to form compound (7).
An example of carboxylic acid derivatives (10) can be produced by reacting the compound (7) obtained by the procedures described above with a compound (8) in the presence of t-BuOK to convert the compound (7) into a compound (9), isomerizing the compound (9) with benzenesulfinic acid, and then hydrolyzing it in the presence of an alkali such as KOH and NaOH. The compound (8) mentioned above can readily be obtained by passing through the Wittig reaction of a corresponding cyclohexanone derivative with MOTP, catalytic hydrogenation in the presence of a catalyst such as Pd-C or Raney-Ni, demethylation reaction with (CH3)3SiI or AlCl3, halogenation with hydrobromic acid, hydriodic acid, or the like, and reaction with triphenylphosphine in turn.
As shown in scheme 2, an example of carboxylic acid derivatives (12) can be produced by subjecting compound (11) and the compound (8) to the Wittig reaction, isomerizing the product, and then hydrolyzing the isomerized product with an alkali. 
wherein Ra has the same meaning as described above, X represents a halogen atom, n is an integer of 0 to 2, and o is 0 or 1.
As shown in scheme 3, an example of carboxylic acid derivatives (14) can also be produced from compound (7) in the same manner as in scheme 1 with the exception that a compound (8) is replaced by a compound (13). Compound (13) can readily be obtained by preparing a Grignard reagent from a corresponding halide, and then passing through formylation with N-formylpiperidine or the like, reduction with sodium boron hydride or the like, halogenation, and reaction with triphenylphosphine in turn.
As shown in scheme 4, an example of carboxylic acid derivatives (15) can also be produced from compound (11) in the same manner as in scheme 2 with the exception that a compound (8) is replaced by a compound (13). 
wherein Ra has the same meaning as described above, X represents a halogen atom, n is an integer of 0 to 2, and o is 0 or 1.
Production of alcohol derivatives:
As shown in scheme 5, compound (16) is converted into compound (17) by introducing a protective group such as tetrahydropyranyl group and then reacted with an organic lithium reagent such as n-butyl lithium, and iodine to convert into compound (18). Phenol derivative (19) which is an example of the alcohol derivatives can be obtained by cyanogenating the compound (18) and then deprotecting the cyanogenated compound.
As shown in scheme 6, phenol derivative (21) which is an example of the alcohol derivatives can also be obtained by reacting the compound (18) mentioned above with sodium trifluoroacetate/copper iodide (I) (G. E. Carr et al., Journal of the Chemical Society, Perkin Trans Reactions I, 921, (1988)) or methyl fluorosulfonyldifluoroacetate/copper iodide (I) (Q, Y. Chen et al., Journal of the Chemical Society, Chemical communications, 705 (1989)) to convert into compound (20), and then deprotecting this compound.
As shown in scheme 7, the compound (17) mentioned above is reacted with an organic lithium reagent such as n-butyl lithium and phenyl lithium, and formylating agent such as N-formylpiperadine (G. A. Olah et al., Angew. Chem., International Edition in English, 20, 878 (1981)), N-formylmorpholine (G. A. Olah et al., The Journal of Organic Chemistry, 49, 385 (1984)), and DMF (G. Boss et al., Chemische Berichte, 1199 (1989)) to convert into compound (22), and the compound (22) is reacted with a fluorinating agent such as diethylaminosulfurtrifluoride (DAST) (W. J. Middleton et al., The Journal of Organic Chemistry, 40, 574 (1975); S. Rozen et al., Tetrahedron Letters, 41, 111 (1985); M. Hudlicky, Organic Reactions, 35, 513 (1988); P. A. Messina et al., Journal of Fluorine Chemistry, 42, 137 (1989)) to convert into compound (23). Phenol derivative (24) which is an example of the alcohol derivatives can also be obtained by deprotecting the compound (23).
As shown in scheme 8, the compound (22) mentioned above is reduced by a reducing agent such as sodium boron hydride (SBH), lithium aluminum hydride (LAH), diisobutyl aluminum hydride (DIBAL), and sodium bis(2-methoxyethoxy)aluminum hydride (SBMEA) to convert into compound (25), and the compound (25) is reacted with a fluorinating agent such as DAST to convert into compound (26). Phenol derivative (27) which is an example of the alcohol derivatives can also be obtained by deprotecting the compound (26). 
As shown in scheme 9, compound (28) is treated in the presence of nitric acid and sulfuric acid to convert into compound (29) and then converted into xanthate by the method of Albert et al. (Synthetic Communications, 19, 547 (1989)). Phenol derivative (31) which is an example of the alcohol derivatives can also be obtained by fluorinating the xanthate by the method of Kurohoshi et al., (Tetrahedron Letters, 33, 29, 4173 (1992)), subjecting to a catalytic hydrogen reduction in the presence of a platinum catalyst to convert into compound (30), reacting with hydrochloric acid and sodium nitrite, and then hydrolyzing the resulting diazonium salt.
Further, as shown in scheme 10, the compound (29) mentioned above is fluorinated in a system of chlorodifluoromethane/sodium hydroxide (cf. WO Japanese Patent Publication (Tokuhyo) No. Hei 3-500413) and then subjecting the product thus obtained to a catalytic hydrogen reduction in the presence of a platinum catalyst to convert into compound (32). Phenol derivative (33) which is an example of the alcohol derivatives can also be obtained by reacting the compound (32) obtained by the procedure described above with hydrochloric acid and sodium nitrite, and then hydrolyzing the resulting diazonium salt. 
While examples of production methods are described with typical compounds of the present invention, it goes without saying that other compounds of the present invention can readily be produced, for instance, by using other known reactions in combination in addition to the reactions used in the production methods described above.
Introduction of double bond or ester bond is sufficiently performed not only at the final stage of the reactions but also at a selected suitable time.
Liquid crystalline compounds of the present invention thus obtained have a wide temperature range of liquid crystal phase, low viscosity, low threshold voltage (V10), and excellent stability, and are readily mixed with various liquid crystal materials and good in solubility at low temperatures. Also, the compounds of the present invention are sufficiently stable chemically and physically under conditions in which liquid crystal display devices are ordinarily used and thus are remarkably excellent as component of nematic liquid crystal compositions.
Compounds of the present invention can preferably be used as component in liquid crystal compositions for TN mode, STN mode, or TFT mode.
Compounds of the present invention having three rings exhibit a wide temperature range of liquid crystal phase and a comparatively low viscosity, and the compounds having four rings exhibit a wider temperature range of liquid crystal phase and a particularly high phase transition temperature to isotropic phase.
The compounds of the present invention having two or more cyclohexane rings in the molecule exhibit a low xcex94n and a low viscosity, and the compounds having two or more aromatic rings exhibit an especially wide temperature range of liquid crystal phase, a particularly high phase transition temperature to isotropic phase, and a high xcex94n.
Compounds of the present invention having pyridine ring, pyrimidine ring, or dioxane ring exhibit a comparatively high xcex94xcex5.
Since the compounds of the present invention have a large elastic constant ratio, it is possible to make the change in transmission of liquid crystal compositions steep and thus liquid crystal display devices having a high contrast can be provided by using the compounds as component of liquid crystal compositions for STN.
Besides, the compounds can be modified toward more preferable ones as component for STN by introducing double bond in Ra and/or Rb in the formula described above.
Compounds particularly important as chiral dopant can be provided when the Ra and/or Rb is an optically active group.
When the Rb is a halogen atom, halogen substituted alkyl group, or halogen substituted alkoxy group, compounds having a high xcex94xcex5; and when the Rb is cyano group, compounds exhibiting an especially high xcex94xcex5 can be provided, respectively.
By substituting fluorine atom for the hydrogen atom in the ring structure, the compounds can be converted into ones having a higher xcex94xcex5 and an improved mutual solubility.
When triple bond is introduced in Z1, Z2, or Z3 in the formula described above, compounds exhibiting a high xcex94n can be obtained.
As described above, new liquid crystalline compounds having desired physical properties can be obtained by selecting proper rings, substituents and/or bonding groups in the compounds of the present invention expressed by the general formula (1). At that time, each element in the compounds may be selected from their isotope.
While the liquid crystal compositions provided by the present invention may be comprised of only a first component comprising at least one liquid crystalline compound expressed by the general formula (1), the compositions preferably comprise, as a second component, at least one compound (hereinafter referred to as second component A) selected from the group consisting of the compounds expressed by any one of the general formulas (2), (3), and (4) described above and/or at least one compound (hereinafter referred to as second component B) selected from the group consisting of the compounds expressed by any one of the general formulas (5), (6), (7), (8), and (9) in addition to the first component, and further, the compositions may comprise, as a third component, a known compound for the purpose of adjusting V10, temperature range of liquid crystal phase, xcex94n, xcex94xcex5, or viscosity.
Among the second component A, compounds of the formulas (2-1) to (2-15) can be mentioned as preferable examples of the compounds included in the general formula (2); compounds of the formulas (3-1) to (3-48) can be mentioned as preferable examples of the compounds included in the general formula (3); and compounds of the formulas (4-1) to (4-55) can be mentioned as preferable examples of the compounds included in the general formula (4), respectively. 
Compounds expressed by one of the general formulas (2) to (4) exhibit a positive xcex94xcex5 and are excellent in heat stability and chemical stability.
Amount of the compounds to be used is suitably in the range of 1 to 99% by weight, preferably 10 to 97% by weight, and more desirably 40 to 95% by weight based on the total amount of liquid crystal composition.
Among the second component B, compounds of the formulas (5-1) to (5-24), (6-1) to (6-3), and (7-1) to (7-28) can be mentioned as preferable examples of the compounds included in the general formula (5), (6), and (7), respectively. 
Compounds expressed by one of the general formulas (5) to (7) have a large positive xcex94xcex5 and are used as a component of liquid crystal compositions particularly for the purpose of lowering V10. The compounds are also used for the purpose of adjusting viscosity, adjusting xcex94n, or widening temperature range of liquid crystal phase, and further for the purpose of improving th steepness.
Among the second component B, the compounds of the formula (8-1) to (8-8), and (9-1) to (9-13) can be mentioned as preferable examples of the compounds included in the general formula (8) or (9). 
Compounds expressed by the general formula (8) or (9) have a negative or a small positive xcex94xcex5 value. Among them, the compounds expressed by the general formula (8) are used as a component of liquid crystal compositions principally for the purpose of reducing viscosity and adjusting xcex94n, and the compounds expressed by the general formula (9) are used for the purpose of widening temperature range of liquid crystal phase and/or for the purpose of adjusting xcex94n.
Compounds expressed by one of the general formulas (5) to (9) are indispensable particularly when liquid crystal compositions for STN display mode or ordinary TN display mode are produced. Amount of the compounds to be used is suitably in the range of 1 to 99% by weight, preferably 10 to 97% by weight, and 40 to 95% by weight based on the total amount of liquid crystal composition when liquid crystal compositions for ordinary STN display mode or TN display mode are produced.
Liquid crystal compositions provided according to the present invention preferably comprise at least one liquid crystalline compound expressed by the general formula (1) in the ratio of 0.1 to 99% by weight to develop excellent properties.
The liquid crystal compositions are usually produced by methods which are known by themselves, for instance, by a method in which various components are dissolved each other at a high temperature. Moreover, the liquid crystal compositions are improved and optimized depending on intended uses by adding a suitable additive, when necessary. Such an additive is well known in the art and described in detail in the literature. Usually, a chiral dopant or the like is added to induce a helical structure of liquid crystals thereby adjust a required twisting angle and avoid a reverse-twist. As its examples, optically active compounds expressed by one of the following formulas (Op-1) to (Op-8) can be mentioned. 
Liquid crystal compositions of the present invention can be used as ones for GH (guest-host) mode by adding a dichroic dye such as merocyanine type, styryl type, azo type, azomethine type, azoxy type, quinophthalone type, anthraquinone type, or tetrazine type dye. Liquid crystal compositions of the present invention can also be used as liquid crystal compositions for NCAP which is prepared by the microencapsulation of a nematic liquid crystal, or for polymer dispersed liquid crystal display devices (PDLCD) which are prepared by forming in the liquid crystal a three-dimesnsional network structure of a polymer, for example, polymer network liquid crystal display devices (PNLCD) as well as for electrically controlled birefringence (ECB) mode or dynamic scattering (DS) mode.
Liquid crystal compositions of the present invention are produced by the methods as described above, and the following Composition Examples 1 through 33 can be shown as examples of the compositions.
In the composition examples, compounds are designated by the abbreviation according to the definitions shown in the following Table 1. Specifically, left hand side terminal group is indicated by n-, nO-, Vn-, nVm-, or nVmVk- (n, m, and k are an integer of 1 or more); bonding group is indicated by 2, E, T, V, or CF20; ring structure is indicated by B, B(F), B(F,F), H, Py, D, or Ch; right hand side terminal group is indicated by xe2x80x94F, xe2x80x94CL, xe2x80x94C, xe2x80x94CF3, xe2x80x94OCF3, xe2x80x94OCF2H, -n, -On, or -Eme (n is an integer of 1 or more). Number of compound affixed to the compounds of the present invention is the same as that shown in Examples below.